Generally, golf balls are roughly classified into a thread wound golf ball and a solid golf ball. The thread wound golf ball is produced by winding a thread rubber onto a liquid center comprising a liquid enclosed in a rubber ball or a solid center comprising a crosslinked molded article of a rubber composition at a highly stretched condition to form a thread wound core and then covering the thread wound core with a cover. The solid golf bail includes two-piece solid golf balls or three piece golf balls, produced by covering a solid core comprising a crosslinked molded article having a one- or two-layer structure with a cover, and a one-piece solid golf ball comprising an integrally molded crosslinked article of a rubber composition.
Among them, the two-piece and three-piece solid golf balls have recently, exclusively been used as a golf ball because of there particular long flying distance.
However, the two-piece and three-piece solid golf balls have a drawback in that the hit feeling is hard and inferior in comparison with the thread wound golf ball.
Therefore, in order to improve the drawback of the two-piece and three-piece solid golf balls, a trial of softening the core which makes the ball softer towards its center to increase deformation of the golf ball upon hitting have been studied (e.g. Japanese Laid-Open Patent Publication No. 4 (1992)-109971, etc.).
However, the durability and resilient performances (flying distance) are deteriorated by softening the core.
On the other hand, the one-piece golf ball is mainly used as the golf ball for driving ranges, and in such use, cracking and chipping of the ball surface tend to be caused by repeated hitting in this application. Therefore, excellent durability is particularly necessary for the one-piece golf ball.